Types of Defects and Reactions

When Ce02 is reduced to Ce02.x, defects are created in the form of Ce, which in the Kroger-Vink-notation is written as Ce ce as the Ce has one negative charge compared to the normal lattice In early works it was discussed whether these substitutional negative defects were balanced by some of the Ce going on interstitial sites as Ce or by oxide ion vacancies, V o. Later works appear to 

Oxide vacancies may also be introduced by doping with oxides of metals with lower valences, e.g. by dissolution of CaO or 00203  

Already existing oxide vacancies may be removed by doping with oxides of higher valency than 4  

Reaction (15.1) may also take place in doped ceria, and doping will naturally affect the equilibrium of reaction (15.1) by changing the concentration of oxide vacancies and by decreasing the concentration of Cccg. 

Assuming no interaction between the various defects (only valid for very low concentrations) the law of mass action is valid. Applied on eq.(15.1) it gives  

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